An apparent pattern in history is that civilisations based on temperate zone farmers (Classical, Western, Japanese) seem to have developed institutions which proved to be more adaptable in the long term than civilisations based on river valleys which periodically get conquered by mounted pastoralists (Achaemenid Persia and predecessors, Islam, Northern India, China) with Russia--a temperate zone farming civilisation which was conqured/ravaged by mounted pastoralists--as an intermediate case.
I am interested in identifying differences between medieval Europe and medieval Japan that can be traced to either religious differences (specifically, Japan not being Christian) or medieval Europe's Classical heritage.
The ones that strike me are (1) suicide. The Christian prohibition of suicide seems to me the most obvious difference in social attitudes, particularly the difference between
chivalry and
bushido.
And (2) deliberative assemblies. Japan had advisory councils which were close-ish in some ways, but it did not develop anything like the Cortes, Parliament, Estates-Generals, Diets etc of Medieval Europe. The examples of the Roman Senate and Athenian Assembly--via surviving Classical texts--along with Germanic warrior assemblies, seems to me to have been the origins of the medieval development of deliberative assemblies (though including elected representatives is a
medieval innovation).
Any other suggestions?